A conventional cellular network is deployed as a homogenous network of macrocell base stations. The macrocell base stations may all have similar antenna patterns and similar high-level transmit powers. To accommodate increases in data traffic, more macrocell base stations can be deployed in a homogenous network, but such a solution is often unattractive due to increased inter-cell interference on the downlink and due to the high costs associated with site acquisition for newly deployed macrocell base stations.
Because of these drawbacks, cellular network operators are turning to heterogeneous networks to meet the demands of increased data traffic. In heterogeneous networks, small cell base stations are used to provide small coverage areas that overlap with the comparatively larger coverage areas provided by macrocell base stations. The small coverage areas are specifically provided in areas with high data traffic (or so called hotspots) to increase capacity. Examples of small cell base stations include, in order of decreasing coverage area, microcell base stations, picocell base stations, and femtocell base stations or home base stations. Small cells deployments result in more base stations that are closer to the mobile devices they serve. The increased network capacity of small cells make them a promising solution to deliver 5G throughput.
Some modern cellular standards, such as the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), employ single frequency reuse (SFR), where each cell in the network operates on the same frequency. Interference management can be a problem in small cell deployments on SFR networks due to proximity of the cells. For example, small cells can be deployed in adjacent rooms of a building. In such a scenario, the signals emitted from a base station may penetrate into an adjacent cell, causing inter-cell interference to receivers in the adjacent cell.
To address inter-cell interference in small cell deployments, the 3GPP Working Group developed enhanced inter-cell interference coordination (eICIC), which enables time-domain coordination between base stations where dominating interfering cells are present. In eICIC, adjacent base stations coordinate to occasionally transmit an almost blank subframe (ABS). This coordination typically requires real-time communication between the base stations via a high-speed X2 interface. It would therefore be beneficial to enable eICIC with minimal or no real-time coordination between base stations.